Greetings,

I am working on a troubleshooting simulator and I have no experience regarding multimeters.
First of all, if I'm measuring the voltage for a resistor for example, how does the multimeter reads the measurement? does the multimeter's resistance draw small current and calculate the the voltage across it's resistance(MM internal resistance) ?! is this how it works ?!!

 

At a very basic level, yes. But the "calculation" is a bit more complex.

https://en.wikipedia.org/wiki/Analog-to-digital_converter

ak

 

Greetings,
I am working on a troubleshooting simulator and I have no experience regarding multimeters.
First of all, if I'm measuring the voltage for a resistor for example, how does the multimeter reads the measurement? does the multimeter's resistance draw small current and calculate the the voltage across it's resistance(MM internal resistance) ?! is this how it works ?!!

yes it is....

mentioned ADC is just key component when MM is digital type.
circuitry of digital MM ensured high internal resistance (so current through MM is really really small).

in analog MM, internal resistance is significantly lower (usually current is driving galvanometer directly, without amplification), therefore current through analog MM is generally significantly larger than through digital MM.

 

At a very basic level, yes. But the "calculation" is a bit more complex.

https://en.wikipedia.org/wiki/Analog-to-digital_converter

ak

Thanks for the help, but you miss understood me. I was asking about the circuit,like how is the current from the 'live circuit' going into the MM circuit?

 

It goes in one wire, through an internal 10 megohm resistor, and out the other wire. Most digital multimeters have a 10 megohm input impedance. This actually is a string of several resistors in series that add up to 10M or more. As you change the meter range, it connects to the resistor string at different points along the series. The effect is that to an external circuit, the meter input looks like a 10M resistor no matter which range the meter is set to. Internally, the incoming signal is not attenuated, or attenuated by 10, 100, or 1000.

https://www.eleccircuit.com/digital-multimeter-circuit-using-icl7107/

ak

 

Thanks for the help, but you miss understood me. I was asking about the circuit,like how is the current from the 'live circuit' going into the MM circuit?

It just measures the voltage (not current) directly across the resistor with an A/D converter, if it's a digital meter.
The resistor current does not go into the meter, other than a very small amount from its input resistance (typically 10 megohms).
The meter input resistance is just to provide a known load across the meter input to what is being measured, it otherwise is not involved in the measurement.

Do you understand the difference between voltage and current?
Voltage appears across a resistor (or other component).
Current is what flows through the resistor resistance due to the voltage across it as determined by Ohm's law, I = V / R.